This invention relates generally to watermarking, and more particularly to fragile watermarking for objects.
With the increasingly popularity of computers, and with the advent of mass networks such as the Internet, electronic distribution of content, such as images, sounds and three-dimensional objects, has become much more common. However, electronic content distribution has raised concerns for the creators of such content. For example, content creators desirably wish to ensure that copyright and other authorship and ownership information is attached to their electronic content, such that subsequent attempts to determine the author and owner of the content are successful. Furthermore, the creators desirably wish to determine that their content has not been altered since first being distributed electronically.
To achieve these goals, a prior art solution is to include a header or other secondary file to the file containing the electronic content. However, this solution has disadvantages. If the header or other secondary file is not subsequently distributed with the file containing the electronic content, then all the information contained in the header or other secondary file is lost. Thus, programmers have sought to engrain the information directly into the content file itself, within the content itself, such that the information is not easily removed, and such that the information is hidden within the content, and not easily discerned without a key.
This embedding of hidden data into electronic content is generally known as digital watermarking. Digital watermarking is generally divided into two types of watermarking: robust watermarking and fragile watermarking. Robust watermarking attempts to embed information into electronic content in such a manner that subsequent attempts to rid the electronic content of the watermark, or less malicious digital processing such as applications of various compression schemes, do not remove the watermark from the electronic content. In other words, the watermarking is robust in that survivability of the watermark within the electronic content is the primary consideration.
Conversely, fragile watermarking attempts to embed information into electronic content in such a manner that subsequent attempts to rid the electronic content of the watermark specifically reflect the attempts to alter the electronic content. Thus, fragile watermarking is used in situations where the integrity of the original electronic content is important, such that attempts to subsequently alter the content are desirably easily discerned. This compares with robust watermarking, where the survivability or robustness of the watermark within the content is a main concern. In fragile watermarking, the watermark is typically sensitive for the subsequent detection of any unauthorized changes in content and the locations of change. Additionally, an important issue is that the watermarking scheme should desirably be resistant against attacksxe2x80x94attacks aiming to decode the watermark, or forge the watermark after unauthorized alterations. These pose as special requirements for fragile watermarking that the other watermarking techniques within the prior art have generally not been able to address adequately.
Fragile watermarking and robust watermarking, because of their different goals, employ different considerations in programming schemes to achieve their respective goals. That is, a scheme for robust watermarking is typically not applicable in the context of fragile watermarking, and vice-versa. In other words, the existence of one type of watermarking scheme for a given type of digital dataxe2x80x94e.g., image data or sound dataxe2x80x94does not usually assist the development of a corollary scheme for the other type of watermarking scheme.
Watermarking is also divided into public and private schemes of watermarking. A public watermarking scheme provides for detection of the watermark without the original electronic content, whereas a private watermarking scheme does not provide for watermark detection without the original content. As in the case of fragile and robust watermarking, a scheme for public watermarking is generally not applicable in the context of private watermarking, and vice-versa. Thus, the existence of a public watermarking scheme for a given type of digital data does not usually assist the development of a corollary private watermarking scheme, and vice-versa.
Furthermore, different models for watermarking are generally applicable to different types of content. Thus, a watermarking model for images is not usually applicable to three-dimensional objects or sounds. Here again, the existence of a watermarking scheme for a given type of digital data does not usually assist the development of a corollary watermarking scheme for a different type of digital data. A watermarking scheme for images, in other words, does not usually point to a similar scheme for sounds or other digital data.
Thus, there is a desire for fragile watermarking of three-dimensional objects. With the increasing speed of computers, more content creators have access to technology that allows for the creation of such three-dimensional objects. The increase in the creation and distribution of three-dimensional objects has also occurred because of the relatively recent existence of a file format standard for such objects, such as various versions of the Virtual Reality Markup Language (VRML), for example, as described in the International Standard Organization (ISO) reference entitled xe2x80x9cInternational Standard ISO/IEC 14772-1:1997xe2x80x9d. Thus, the need for authors of such three-dimensional objects to detect subsequent changes of their work in a manner that fragile watermarking allows is apparent.
The present invention relates to fragile watermarking for three-dimensional objects. In one embodiment of the invention, a computerized system includes an encoder and a decoder. The encoder is operative to encode a watermark into an object, such as a three-dimensional object, in a fragile manner (viz., in a manner to provide for fragile watermarking, as has been described in the background), utilizing a key. Desirably, the key and the watermark are kept secret. The decoder is operative to decode the watermark from the object in which the watermark is encoded in a public manner, also utilizing a key. In addition to this embodiment, other embodiments of the invention include computerized systems, methods, computers, and media of varying scope.